go/pacakges: remove some todos

* use std slices.Clip
* remove outdated check as the original issue was fixed

Change-Id: Ie54b202ecabc3318a4f20772fd62bd63542f8237
Reviewed-on: https://go-review.googlesource.com/c/tools/+/626416
Reviewed-by: Michael Matloob <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Alan Donovan <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>

go/packages/external.go

@@ -13,6 +13,7 @@ import (
 	"fmt"
 	"os"
 	"os/exec"
+	"slices"
 	"strings"
 )
 
@@ -131,7 +132,7 @@ func findExternalDriver(cfg *Config) driver {
 		// command.
 		//
 		// (See similar trick in Invocation.run in ../../internal/gocommand/invoke.go)
-		cmd.Env = append(slicesClip(cfg.Env), "PWD="+cfg.Dir)
+		cmd.Env = append(slices.Clip(cfg.Env), "PWD="+cfg.Dir)
 		cmd.Stdin = bytes.NewReader(req)
 		cmd.Stdout = buf
 		cmd.Stderr = stderr
@@ -150,7 +151,3 @@ func findExternalDriver(cfg *Config) driver {
 		return &response, nil
 	}
 }
-
-// slicesClip removes unused capacity from the slice, returning s[:len(s):len(s)].
-// TODO(adonovan): use go1.21 slices.Clip.
-func slicesClip[S ~[]E, E any](s S) S { return s[:len(s):len(s)] }

go/packages/packages_test.go

@@ -511,11 +511,6 @@ func testConfigDir(t *testing.T, exporter packagestest.Exporter) {
 				test.dir, test.pattern, got, test.want)
 		}
 		if fails != test.fails {
-			// TODO: remove when go#28023 is fixed
-			if test.fails && strings.HasPrefix(test.pattern, "./") && exporter == packagestest.Modules {
-				// Currently go list in module mode does not handle missing directories correctly.
-				continue
-			}
 			t.Errorf("dir %q, pattern %q: error %v, want %v",
 				test.dir, test.pattern, fails, test.fails)
 		}